Alright, more accurately the use of the term stereotype in the sense of an oversimplified generalization about a particular type of person or thing is less than a century old. Walter Lippmann's classic text Public Opinion – read it and you'll feel like it was written last year rather than during World War I – debuted the term to the mass public. Oddly enough, though, he drops it in the text cold without introducing or defining it, leaving open the possibility that the term may already have been circulating in literate circles at the time. Alternatively he may simply have assumed that readers could understand it from context. So the follow-up question is: Where did Lippmann get it from? He certainly was a great writer. Perhaps he just made it up?

Not exactly. Stereotype was the name of a printing process invented in 1795 by a Frenchman named Firmin Didot, the son of the man who invented the Didot typeface for those of you who are into such things. Firmin coined it, as was the style of the time, by combining two Latin terms: stereo (solid) and typos (impression). Therefore in the literal sense a stereotype is a solid impression of a group of people. "Solid" in this case has no positive connotation (e.g., "a solid victory" or "do me a solid brah") but to its firmness and lack of variation. The stereotype printing process involved a means of reproducing printing plates efficiently and then using the reproduced (stereotyped) plates to print rather than the original. This allowed extremely consistent printing at a good rate of production, and Didot was very successful. In short, he pioneered a process of churning out unvarying, nearly identical copies of a single source.

I have no idea how or why Walter Lippmann was acquainted with the technical details of antiquated French printing processes. It is inarguable that the term is uniquely suited to conveying the spirit and concept of the modern use of the word.